Chapter 8. Cloning Systems

Setting up a cluster means setting up machines-hopefully, lots of machines. While you should begin with a very small number of machines as you figure out what you want, eventually you'll get to the point where you are mindlessly installing system after system. Fortunately, most of those machines will have identical setups. You could simply repeat the process for each machine, but this will be both error prone and immensely boring. You need a way to automate the process.

The approach you need depends on the number of machines to be set up and configured, the variety of machines, how mission critical the cluster is, and your level of patience. For three or four machines, a manual install and configuration of each machine is a reasonable approach, particularly if you are working with an odd mix of different machines so that each setup is different. But even with a very small number of machines, the process will go more smoothly if you can automate some of the post-installation tasks such as copying configuration files.

Unless you have the patience of Job, with more than eight or ten machines in your cluster, you'll want to automate as much of the process as possible. And as your cluster's continuous operation becomes more crucial, the need for an automated approach becomes even more important.

This chapter begins with a quick look at simple approaches to ease configuring multiple systems after the operating system has been installed. These techniques are useful for any size cluster. Even if you are clearly in the fully automated camp, you should still skim this section since these techniques apply to maintaining clusters as well as setting up clusters.

Next, three tools that are useful when building larger clusters are described-Kickstart, g4u (ghost for Unix), and SystemImager (part of the Systems Installation Suite). These tools are representative of three different approaches that can be used. Kickstart is a package-based installation program that allows you to automate the installation of the operating system. g4u is a simple image-based program that allows you to copy and distribute disk images. SystemImager is a more versatile set of tools with capabilities that extend beyond installing systems. The tools in SystemImager allow you to build, clone, and configure a system. While these tools vary in scope, each does what it was designed to do quite well. There are many other tools not discussed here.